Jupiter DIRECT - Livestream Discussion - Sat 11/11/2023

[JAFO]

Chuck and I are going to discuss a possible book later this week. Far too early to promise anything on that front, but we're going to talk and see where it leads us.

Obviously, we'll bring Philip and Steve in to the conversation too, but if any of the other members of DIRECT - either public or private side - would be at all interested in contributing to such an effort, please do drop me a line.

If such a project really does goes ahead, I'll mention it here on NSF.

Ross.

Any word? My credit card is ready to help crowdfund it.

Bump. Still willing to be Donor #1 (or +1 if others beat me) to crowd fund the book.

[kraisee]

Really appreciate the encouragement, but there hasn't been any traction at our end so I just don't see it happening.

Ross.

[JAFO]

Really appreciate the encouragement, but there hasn't been any traction at our end so I just don't see it happening.

Ross.

:sad:

But Thanks for the livestream at least.

[Eric Hedman]

Really appreciate the encouragement, but there hasn't been any traction at our end so I just don't see it happening.

Ross.

:sad:

But Thanks for the livestream at least.

As fascinating as a good history of Direct would be, a good comprehensive history of any project this big and complex is a heck of a lot of work.  If notes, e-mails, CAD models, discussions, aren't organized and documented along the way for the purpose of writing a book, reconstructing a history by sorting through a haystack of information including the NSF threads, and talking with the people who were involved becomes very difficult.  It's not surprising that nobody has the time to do this.

[clongton]

<snip> ...and talking with the people who were involved becomes very difficult.  It's not surprising that nobody has the time to do this.

Especially when one considers that the majority of them were design engineers at Boeing, Lockheed and MSFC, who must remain publicly anonymous. To this day, exposure would not be a pleasant experience for them.

[JAFO]

<snip> ...and talking with the people who were involved becomes very difficult.  It's not surprising that nobody has the time to do this.

Especially when one considers that the majority of them were design engineers at Boeing, Lockheed and MSFC, who must remain publicly anonymous. To this day, exposure would not be a pleasant experience for them.

Understood, sad that there is still a threat to these unnamed engineers.


Since the book will never come out, is there any chance you gents (and ladies, etc.,) that were involved could expand on any of the topics covered in the livestream, as you have time/interest/can with out disclosing any identifying information? For instance, the discovery that the ET I-beam did not actually act as a detuning device to mitigate thrust oscillation of the SRBs.

Maybe we could activate a Direct Q&A , or " Stories from Direct" thread?

[Jer]

Was there any discussion of using the TR-106 (or RS-83) instead of the SSME or RS-68?

[clongton]

Was there any discussion of using the TR-106 (or RS-83) instead of the SSME or RS-68?

No it wasn't. The law mandated using existing infrastructure and flight hardware to the extent possible. The RS-83 was a conceptual reusable engine proposed for the Space Launch Initiative (SLI) in the early 2000s. The design never left the developmental phase, as the program was canceled. So it was never a consideration.

[JAFO]

Chuck, could you talk about  the discovery that the ET I-beam did not actually act as a detuning device to mitigate thrust oscillation of the SRBs?

[clongton]

Chuck, could you talk about  the discovery that the ET I-beam did not actually act as a detuning device to mitigate thrust oscillation of the SRBs?

The idea that the External Tank (ET) I-beam in the Space Shuttle program acted as a detuning device for Solid Rocket Booster (SRB) thrust oscillation has been questioned many times over the years. Originally, the I-beam was thought to play a role in damping or mitigating thrust oscillations that were known to cause concerns during Shuttle launches. However, analysis and testing during actual launches revealed that the I-beam itself did not significantly contribute to the reduction of these oscillations. Thrust oscillations from the SRBs, are actually driven by internal motor pressure fluctuations. The I-beam, a structural element was designed to provide strength and stability during the launch, but it did not have the expected impact on mitigating the SRB oscillations. This led to a shift in focus to other methods for controlling these oscillations, including internal motor changes, nozzle design improvements, and advanced damping techniques like tuned mass absorbers​, all in an attempt to smooth the oscillations out at the source. Ultimately it was suspected, but never proven, that the presence of a large reservoir of fluid (propellant) between the SRBs largely contributed to softening these effects. But I am not  the expert on  this subject. The detailed data we had all came from the team of analysists working the project.

In short, the ET I-beam's role in mitigating thrust oscillation was overstated, and other measures, such as nozzle modifications and internal structural changes, were more effective in managing these issues. I don't know much else about this except that this problem was never completely adjudicated, and was a major concern for the Ares-1 CLV design. Sensors onboard the Ares-1 test vehicle indicated that the oscillations could potentially be debilitating to any crew riding that LV, lending weight to the theory that the ET fluid reservoir of the Shuttle stack was the key to oscillation dampening. But again, to my knowledge never proven.

[sdsds]

For the Jupiter design the key aspect of SRB thrust oscillation was that NASA knew the STS hardware solved it somehow. By retaining ET design and manufacturing techniques, and staying at least initially with four-segment boosters, Jupiter-130 could conceivably have flown while Shuttle was still in service. Or at least with no slip in the launch cadence. That seems like a good thing, right? Consider though the implications:

STS-134: May 16, 2011
STS-135: July 21, 2011
Jupiter 1: September 26, 2011
                 ↕
Orion EFT-1: 5 December 2014

The Orion capsule was only ready for an uncrewed LEO test flight (on DIVH) 3 years after what would have been the Jupiter program's "need by" date. Look at that from the perspective of Lockheed-Martin. Doesn't allowing Boeing to muck around with the SLS core design and manufacturing guarantee you the schedule buffer you need? And aren't you willing to trade the low margin External Tank and Jupiter core business for the high margin capsule business?

Specifically on how the Shuttle stack dealt with SRB thrust oscillation, the intertank structures (including the thrust beam) carried the SRB loads into the mass of the propellants. For the SLWT, wiki says the LOX load was ~629 tons and the LH2 load was ~106 tons, so pretty clearly the LOX dynamics dominated. (Details at https://en.wikipedia.org/wiki/Space_Shuttle_external_tank#Intertank for those interested.)

[Rik ISS-fan]

Didn't a lot of the delays in Orion development have to do with more restrictive requirements for the mass of the system. Caused by lower launch capability of the launch vehicle?

[clongton]

Didn't a lot of the delays in Orion development have to do with more restrictive requirements for the mass of the system. Caused by lower launch capability of the launch vehicle?

Delays caused by both reduced funding and by design changes. The design changes were the major contributing factor. Originally, the Atlas and Delta EELVs could have lifted a conceptual Orion to LEO, where it would meet the Altair lander, still mated to the ESU upper stage. But Administrator Griffin insisted that Orion must only be launched on the Ares-1, so as the design was developed, it was - unnecessarily - made too heavy for either EELV. Unfortunately, once it was determined that the RS25 engine was not restartable in space, the J-2X was developed to replace it, but was not powerful enough and now Orion was too heavy for the Ares-1. So it needed a complete redesign, so that the J-2X would work, but the Orion still be too heavy for the EELVs. Political gerrymandering at its finest.